Against the backdrop of global warming and exhaustion of fossil resources, production of chemical products using renewable resources, along with production of biofuels, is recognized as an emerging industry, biorefinery, which is an important means for realizing a low-carbon society, and has attracted keen attention.
However, production of biophenol using renewable resources is less productive as compared to production of lactic acid or ethanol because the metabolic reaction from a raw material saccharide consists of a great many steps. In addition, for the reasons that produced phenol inhibits bacterial proliferation and that phenol is cytotoxic, industrial production of phenol has been considered to be impossible.
Important use of phenol is phenol resins. A phenol resin, which is produced by addition condensation of phenol and aldehyde, is one of the oldest plastics, and with its properties including excellent heat resistance and durability, is used for various purposes, such as an alternative automotive material to metal, a semiconductor seal material, and a circuit board even today. Due to extremely high reactivity of phenol and aldehyde as raw materials and to the complicated three-dimensional network structure of resulting phenol resin polymers, precise structural designing and development into nanomaterials thereof had been considered difficult and so had been application to high-value-added use. However, in recent years, the theory of physical-properties of polymers and the simulation thereof have rapidly developed, and therefore it has gradually become possible to create highly functional materials from phenol resins by refining the network structure. Under the circumstances, the phenol resin production in Japan is also increasing year by year.
The currently employed industrial production process of phenol (cumene process) is a typical energy-consumptive process in the chemical industry using petroleum-derived benzene and propylene as raw materials, and requiring great amounts of solvent and thermal energy. Therefore, in the light of global environment conservation and greenhouse gas reduction, there is an urgent need to develop an environment-conscious, energy saving process that allows production of phenol from renewable resources and can reduce carbon dioxide emissions and waste products, that is, to establish biophenol production technologies.
There have not been reported phenol-producing bacteria in nature so far.
Also, there have not been known recombinant bacteria-based phenol-producing technologies to achieve a practically sufficient phenol productivity.
Tyrosine phenol-lyase is an enzyme that catalyzes synthesis of tyrosine from phenol, pyruvic acid, and ammonia and the reverse reaction thereof (for example, PTL 1). PTL 2, for example, teaches synthesis of tyrosine from phenol, pyruvic acid, and ammonia with the use of tyrosine phenol-lyase derived from members of the family Enterobacteriaceae.
Also, it is known that efficient tyrosine phenol-lyase production can be achieved by transformation of Escherichia coli with tyrosine phenol-lyase genes derived from various living things (PTL 3 to 5).